


Why You Shouldn't Anger An Interdimensional Dream Demon

by TooManyBooksToRead



Category: Gravity Falls, 僕のヒーローアカデミア | Boku no Hero Academia | My Hero Academia
Genre: Bill is very angry, Crossover, Gen, Other Additional Tags to Be Added, character tags will be added as they appear
Language: English
Status: In-Progress
Published: 2019-06-19
Updated: 2020-01-04
Packaged: 2020-05-14 17:01:02
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 4,343
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19277593
Author URL: https://archiveofourown.org/users/TooManyBooksToRead/pseuds/TooManyBooksToRead
Summary: More enraged than usual at the Mystery Twins Bill Cypher throws them into a random dimension with a few monsters hoping they'll die for good. Unfortunately, if he had bothered to check which dimension he was dropping them in he would have known there were plenty of heroes around to help them





	1. What The Hell Dipper

**Author's Note:**

> So this is my psychotic brainchild, take it now and we'll see where it goes.

“This is all your fault!” said Dipper as he ran through the narrow alley pulling Mabel behind him.

“ _My_ fault,” she shouted back as they heard a loud crash somewhere behind them. “Remind me who decided it was a good idea to piss off the overpowered dream demon.”

“Oh shut up!” he yelled as he dodged a pile of trash.

The siblings continued rushing through the streets with no clear destination and the group of monsters behind them slowly catching up as they moved away from the narrow passage towards a more public, hopefully, safer area.

Clearly, Bill had been a lot more offended at their general existence than usual because these were some of the nastier monsters in his arsenal, and that was without taking into account the whole _stranding them in another dimension_ thing. And really, they hadn’t actually wanted to give him any additional reasons to be mad at them, it just so happened that Dipper was a certified expert at putting his foot in his mouth and Mabel didn’t actively try to stop him.

“They’re gaining on us,” said Mabel as they made a sharp turn out of the alley towards an industrial complex.

He dragged her through the streets behind him, carefully peeking over their shoulders to keep track of their attackers as they neared one of the sturdier looking buildings, he stopped for a second examining the warehouse before spotting a high window.

“C’mon let’s try to get the high ground,” he said.

“On it!” she said while pulling out her grappling hook, “Hang on Dipstick!”

Dipper hugged his sister tightly as she aimed the grappling hook, the zip of the line as it flew through the air followed by the sound of glass breaking the only warning he got before they were abruptly pulled up, rushing towards the window.

“Nice shot Mabel!” he said letting go of her as they climbed through the now broken window.

“Thanks!” she replied with an enthusiastic grin. “Where now?”

They had dropped down into what appeared to be a large two-story bodega, the second floor they’d entered through had a balcony railing that showed the first floor and a lot of crates stacked precariously on top of each other. The domed ceiling showed a multitude of exposed beams and in the floor below were scattered worktables, machinery and crates ready for shipment.

Dipper was already halfway through a plan before the main door in the first floor was punched he rushed towards one of the crate stacks closest to the balcony and told Mabel to do the same, so, when the door flew from its hinges a couple of seconds later they were already in position.

He brings fingers to his lips in a shushing motion and peers over the side of the crates, the monsters are about to disperse but they’re also right on the mark. He looks back at his sister points at the crates in front of him and mimics pushing, after a second she nods back and he counts down.

Three, he backs away from the crates.

Two, he sees Mabel do the same, they make eye contact then turn to look forward with determination.

One, he takes a running start and shoves himself against the crates with all his strength until they topple, he sees the second stack fall over the bannister too and wastes no time checking the results of their effort before turning to his twin again.

“Mabel aim for the support beams and swing.” he latches onto her and she does as he instructed.

They swing from the main support beam of the warehouse until they're close to the door then Mabel recalls the hook and for one agony filled second they are in freefall, then she aims for one of the secondary support beams and shoots.

They jolt painfully as their downwards motion is abruptly stopped and Mabel gradually lowers them to the ground.

They bolt as soon as their feet are safely on the solid floor, that trick certainly didn’t get rid of all the monsters, this is soon confirmed by the deafening roar of something behind them as they keep running, their feet pounding into the pavement as they make it out of the industrial area an into a crowded city street.

As they leave turning left toward the crowded intersection the rays of the sun start to turn orange as it sets on the horizon, perched on top of a lamppost a man wearing all black with a strange scarf over his shoulders eyes the pair of kids warily and sets his sights on whatever destruction they seem to be fleeing from. He can already tell it’s gonna be a long night. With that thought, he leaps off his perch and uses his scarf to swing to a nearby building.

After a few more block running with no signs of their pursuers the siblings finally slow down.

"I think we finally lost them," says Dipper trying to catch his breath.

“ _Finally_ ,” exclaims Mabel, leaning her arms on her knees.

“We should still keep moving, at least until we find a place to stay the night,” he says after a second.

“You are no fun DipDop,” says his sister, “You’re right, but you’re still no fun at all.”

The kids keep walking until they reach a residential district and then slow their pace as they wander around searching for a place to hopefully stay the night. Toward the end of the neighbourhood, they come upon a decrepit old house that looks abandoned enough and force their way inside.

Tired they make their way to a half-destroyed couch and sit leaning on each other for support.

“Dip, what are we gonna do?”

Now that the adrenaline is wearing off the full weight of the situation crashes down on them, a sombre mood takes over the usually cheery siblings.

“I dunno Mabel,” he replies after a second, “for now lets sleep, tomorrow we can figure out where we are and hopefully we can go from there.”

“Do you think we’re trapped? Will, we even be able to go back home?” his sister asks desperately.

He turns to look her in the eye and reaches for her hand in the dark.

“I dunno Mabes,” he says softly, “but what I do know is that Grunke Stan and Grunkle Ford won't give up until they find us, so neither should we.”

“Ok.” She gives him a hesitant smile and they hug each other, falling asleep like that on the couch of the abandoned house.

~~~

“Hey, Boss why are there two kids passed out on our couch?”


	2. Why can't things ever not go wrong around them?

Dabi really wasn’t in the mood for whatever bullshit would be going on at the old abandoned house they now called a temporary base, really he was barely in the mood to deal with the more energetic members of the league on a good day and he would rather go back to his own decrepit excuse for an apartment and pass out.

 

But he’d been avoiding them for a while and he was due for a report anyway so he decided to just get it done now and not make Shigaraki mad, their leader was especially unstable after whatever had happened on Kamino, and he wasn’t about to piss off the guy who could disintegrate him with one touch.

 

As he made his way through the industrial complex, weaving through narrow street and back alleys he noted that a lot of the surrounding warehouses seemed to be damaged, nothing too major so probably a fight in the middle of the night, villains didn’t much care for property damage and heroes could only stop so much.

 

He resolved to tell Shigaraki that there was probably a hero fight in the area and they’d need to change hideouts soon, who knows maybe a change of scenery would do them all some good.

 

He opened the back door and made his way to raid the fridge, the house looked abandoned but they ought to have something to eat around here. He was starving, and if he had to wait around for Shigaraki to come back he’d at least help himself to their supplies.

 

He was so engrossed in his search for food – did they really have _nothing_ edible in this dump? That he almost missed the front door slamming open.

 

He looked up to see who’d decided to grace him with their presence, seeing a flash of blue hair he decided to try to push his luck with how much he could annoy him, or at least he intended to before he noticed the pair slumped over on the couch.

 

“Hey Boss, why are two kids sleeping on the couch?” said Dabi.

 

Shigaraki turned to look at the scarred man leaning on the doorway to the kitchen before glancing towards the couch to confirm there was indeed a pair of teenager sleeping on the couch of their base of operations.

 

“You tell me, asshole,” he said scoffing, “since you’ve clearly taken the time to make yourself comfortable I’d assume you’d have an answer for me.”

 

Dabi turned back and continued scouring the kitchen for anything he could eat.

 

“Don’t look at me I’ve been off trying to recruit more people and just came in to give you my report,” he shrugged, “dunno where those two came from but the pantry is empty.”

 

“Well I just came back from the meeting with Giran and we have to wait for everyone else so I can brief you on our next move,” said Shigaraki a very evident frown on his face, he didn’t like this at all, “Who was supposed to be here anyway? Someone was supposed to be on lookout.”

 

“HEY TWICE,” Dabi yelled with as much enthusiasm as he was willing to give, which was admittedly not much.

 

“Shut up idiot,” said Shigaraki walking toward the couch, “you’re gonna wake them up.”

 

“And..?” he said finally making his way over to the living room where the kids were still sleeping soundly.

 

“Do _you_ want to deal with a pair of kids?” asked Shigaraki raising an eyebrow.

 

“Good point,” he lit one of his fingers turning to look at the other man, “Why don’t we take care of it before it becomes a problem?” he asked gesturing to the pair of brunettes blissfully oblivious to their impending doom.

 

Shigaraki thought about it for a moment, he hated kids, they pulled up some rather nasty and confusing emotions he preferred to not acknowledge and he’d really rather be rid of them but they were trying to keep a low profile for a while, fade out of the public consciousness and strike harder when they were better prepared. As much as he wanted to tell Dabi to kill them and be done with it he felt there may be more room to work within this situation.

“No.” he pushed Dabi’s hand away from them, “maybe we could call their parents for a ransom or something, we blew half the grocery funds on medical supplies last week.”

 

“And if that doesn’t work?” Dabi questioned.

 

“Then Toga gets two other average-looking kids she can pretend to be. They look plain enough to blend into a crowd too.” He answered

 

“Whatever you say boss, but that’s still two extra mouths to feed.” He muttered, “And that is if Toga doesn’t come back with another.”

 

Shigaraki opted to ignore him but that was fine really, he made his way around the couch towards the stairs, stepping on broken glass, “There was a big fight a few blocks from here, I’d suggest we relocate soon.”

 

“Hopefully Compress finds a way to get Kurogiri back before then,” said the other as he sat on a chair by the door.

 

Assuming Shigaraki wanted to hear his report during the briefing he left the other man to his brooding before deciding to take a nap away from him.

 

~~~  
  


“Mabel. Mabel wake up,” Dipper’s voice sounded worried like something had happened while they were asleep but she didn’t care. She was so tired.

 

“Five more minutes Dip,” she said before turning to face the back of the couch, when did it become day anyway?

 

“Mabel, we don’t have the time for that,” her brother insisted shaking her shoulder, “you need to wake up _now_.”

 

“Okay, okay. I’m up.” She rubbed her eyes as she sat up, dizzy from the light of the midday sun shining from the window they’d broken to get in. “What is it? Did he find us?” she asked suddenly very much alert.

 

“No. But uhh… we’ve got company,” he said sneaking a glance to his left.

 

Looking over his shoulder Mabel finally noticed the group of people gathered around the couch they’d been sleeping on, she immediately moved closer to Dipper reaching for his hand and squeezing it, drawing comfort from this familiar feeling in a strange place.

 

 _“What are you kids doing here,”_ a man in a black hoodie sitting on a chair next to the couch started speaking and while Mabel couldn’t make out a single word he was saying his tone was enough to clue her in that this was not a friendly type of conversation.

 

She locked eyes with Dipper and they stared at each other for a second, she caught him nodding toward their backpack to her right, she was going to grab it while he started to speak to the people around them. When they had their very limited supplies they could try to make a run for the door.

The few individuals who’d seemed mostly uninterested before paying attention now that the creepy man had spoken, the man leaning on the stair rail perked up and the masked man in the corner seemed to shift his attention towards them.

 

“L-look we mean you no harm,” she heard Dipper speaking next to her.

_“Look, kid,” another voice came from behind them, “answer him nicely and we won't hurt you.”_

 

The faint smell of smoke reached her nose – was something burning? She shook her head trying to clear her mind and focus on what she was doing. Deep breaths. In, out. In, out. Slowly she started shifting away from dipper and toward the other end of the couch

 

She was inching closer to the bag when she caught the gleam of metal to her right, turning towards it she was a blonde girl with an unnerving smile on her face, she wore an oversized sweater over what seemed like a uniform of some kind and held onto a gleaming knife.

 

She froze looking at the knife then making eye contact with the girl, she was staring at her and her brother, it made her feel uneasy.

 

 _“You’re cute,”_ the blonde said suddenly getting very much inside her personal space bubble, _“Tomura can we keep them, they’re cute, I wanna know more about them.”_

Mabel snatched the backpack and scooched away from the blonde, she’d rather put some distance between herself and that knife, she hoped Dipper was doing better than her, but of course, she’d jinxed it.

 

Mere seconds after the thought crossed her mind she heard her brother gasp, and felt him blindly reach out for her hand feeling dread pool in her gut. They surely could’ve had worse luck, at least this dimension sustain life and had what seemed to be humans living here but this situation didn’t give her much hope in the field of actually surviving long enough to be rescued or find our way back home.

 

Reaching out for Dipper she turned to see the man who’d first spoken, his hood had fallen down to reveal his face was covered by a severed hand, and actually, taking a second to look over his shoulder there were at least four more hands laying on the nearby table.

 

She was petrified, whoever this man was he kept a collection of severed hands, and apparently _wore them_ , that was an unhealthy obsession if she’d ever seen one, and it seemed they may soon be joining the crew at the table.

 

“We don’t know where we are,” said her brother, “we just needed a place to stay the night, if you let us go you’ll never see us again.”

 

 _“He looks so scared! It’s adorable.”_ Said the blonde now standing right in front of them.

 

_“Toga can you stay quiet for a second, please,”_

 

The man with hand on his face stood still for a second if she could guess she’d say he looked thoughtful but it was hard to read him with that stupid hand.

 

A tense silence spread through the room Mabel was on edge and she was pretty sure Dipper was too, but now that Knife girl had moved in front of them they had a clear way to run and maybe make a dash for the door. If worse came to worse they could throw something toward the door and make a dash for the window they’d broken to come in.

 

She was about to jump and test their chances at escape when the creepy hand man spoke again, except this time he talked in English, English she could understand. Was their luck finally turning up?

 

“Can you understand me now?” he asked hesitantly, there was a slight hint of an accent but he spoke fluidly and confidently.

  
The twins nodded slowly, still not sure what to make of this new development.

 

 _“They understand English,”_ he said to his companions hurriedly, _“if any of you are fluent enough to speak it switch right now, we’ll fill the rest of the group in later.”_

“Um… can you tell us what’s going on?” she asked hesitantly, “We’re very lost and very confused right now.”

 

“Well you two kind of stumbled into our place, and we want to know how and why.” The scarred man punctuated his statement by lighting a finger on fire and pointing it directly at Dipper’s head.

 

Maybe they had drawn the short straw in dimensions because if Scarface could conjure fire out of nothing there was a high likelihood that everyone in this room had some sort of superpower and oh boy were their chances of leaving in one piece diminishing by the second.

 

Scarface turned out to be the man she’d heard speak while she har hed back turned and he joined the other two in front of them, at some point she’d lost track of the masked one, that wasn’t good. Not good at all.

 

“We don’t want any trouble,” said Dipper cautiously, bless her baby brother taking the lead but it was his mouthing off that had gotten them in this situation in the first place.

 

The two men didn’t look quite convinced and the girl seemed focused on something else but the tension was still there and she decided to take the reins.

                                                                                                                     

“Dipstick let me handle this one,” she said looking at him, “please?”

 

He looked sceptical but didn’t stop her so she took that as her go ahead.

 

“Look my brother and I were attacked, we don’t know where we are or what is going on,” she said nudging the blonde’s hand away from her face, “and as I’m sure you’ve noticed we don’t even know the language. We just need help to find a way back home and if you’ve got a problem with that you can talk to the business end of my grappling hook.”

 

Mabel stood resolutely and dragged Dipper up and closer to her, her other hand moved to her sweater pocket where she always stashed her trusty grappling hook.

 

“If you needed help why haven’t you run to the heroes?” asked the scarred man narrowing his eyes, “a pair of kids squatting in an abandoned house so close to Kamino after the fight. Not very likely.”

 

“You have heroes in this dimension.” Dipper blurted out. “Of course you do, if people have super-powers then superheroes isn’t that far of a reach.” Her brother looked like he was about to slip off the deep end into his own thoughts.

 

Mabel felt the urge to facepalm, she loved her brother she really did but as the one who was fond of forethought and planning, he really lacked a brain to mouth filter sometimes. It was after all what had gotten them here in the first place, Cypher deserved it but that still didn’t make it a smart move.

 

“Did you just say dimension?” asked the severed hand man.

 

She thought he sounded confused but the stupid hand – why the hell did he even use it as a mask? – made it impossible for her to read him it was annoying.

 

Looking to the other side Knife girl had moved over the back of the couch and was now cooing over her brother’s thinking face, leaning uncomfortably close to his face and still loosely holding the very sharp knife pointed in his direction.

 

Mabel didn’t waste any time. She pulled out her grappling hook and shot towards the window, then taking advantage of the second of distraction from the other group bolted toward the door dragging Dipper with her.

 

The pull on his arm was enough to snap him out of his train of thought and they ran across the living room towards their escape, he glanced over his shoulder to confirm they were indeed being chased.

 

“Any ideas on how to shake them off?” Mabel asked her brother before making a sharp right to avoid a stream of fire.

 

“We could try the rooftops and improvise,” he said pointing at the edge of a flat-topped roof.

 

For the second time since they’d been dropped in this dimension, they zipped upwards before climbing on the roof and dashing for the ledge to make the jump to the next house it wasn’t their best plan but it was definitely better than their run-in with almost all of the improbable creatures that roamed around the woods of Gravity Falls.

 

Mabel clutched Dipper’s hand harder as they kept rushing through the rooftops, she could spot the Knife girl and the masked man giving chase behind them. No sign of Hand-man or Scarface anywhere, that wasn’t good.

 

They were just about to make a jump from a terrace to a nearby overhang when a knife flew past them unnervingly close to her brother’s face. People who missed were never that close to the target, or maybe it mas just their shit luck she thought as they made the jump.

 

She could hear the pad of footsteps, a lot of them, way more than what two – four if Scarface and Hand-man joined their friends – people would suggest. So of course. That’s when she turned around to find that on not only were all four of them following them, there were at least two extra copies of the girl. Because they couldn’t have anything nice in this world apparently.

 

“Dipper what do we do?” she asked because Dipper was the plan guy if anyone could get them out of this one it would be him. “Maybe water? Wasn’t that how all your clones died?” she continued desperately.

 

“I don’t think it works the same way here Mabel.” He said backing up toward the edge of the roof.

 

The copies of the girl approached slowly like a hunter trying not to scare off its prey as it stalked closer, she was smiling, all three of her were smiling but it was unnerving. The too-wide smile showed her glimpses of fangs that only made her unease worse.

 

Behind her, she could see the masked man who seemed to be caught in between expressions of pure outrage and joy, switching dramatically between them, Scarface and Hand-man were there too walking at a much more leisurely pace while still keeping a threatening posture, it kind of reminded her of Wendy whenever she was with the rest of her family, very clearly bored but also aware of everything around her.

 

“Wanna play?” Kife girl’s voice was as cutting as her weapons, with a very pronounced accent that coupled with the look in her eye reminded her of Cypher.

 

She shivered and edged closer to the drop.

 

“Mabel, please trust me.” She heard Dipper say as he looked over his shoulder.

 

And that was definitely his I’m about to do something crazy and stupid voice but they didn't have very many choices at the moment so instead of trying to argue – she was the reckless twin anyway.

 

Their moment was unfortunately interrupted as the next of the girl’s knives _didn’t_ miss its mark. For a single second all she could see was her brother's face, frozen in pain from the knife that had just embedded itself on his leg his scream echoing in the emptiness of the neighbourhood.

 

Then everything came into sharp focus especially the smile on the girl’s face, Mable didn’t hear anything anymore, she saw red and the next thing she knew she’d punched one of the clones in the face and shot her grappling hook through Scarface’s stomach.

 

Out of the corner of her eye, she catches sight of another of the girls approaching her downed brother and with renewed fury runs to intercept her tackling her to the ground they roll on the roof trying to pin each other down and suddenly there is no roof under them anymore and gravity is catching up to her, she tries to trigger her grappling hook but it chooses exactly that moment to jam because _of course it does_.

 

And just as she’s contemplating what the other side might be like a hand catches hers, and it just had to be Dipper who looks pale and like he’s lost too much blood to even attempt to hold both of them up, much less fight against however many people are still up there.

 

And then as if their day could get any worse she hears the one voice she least wished to hear at the moment.

 

“Why if it isn’t Shooting Star and Pine Tree! Just who I wanted to see!”

**Author's Note:**

> The twins have a fun dynamic, hopefully, I'm conveying it right. Who was the mysterious stranger? You'll find out at some point.  
> Thanks for reading this whatever it turns out to be, any comments or constructive criticism is appreciated as I'm still learning.


End file.
